The invention relates generally to air filtration devices, and more particularly to air filters with filtration media surrounding an internal rigid support that can be removed from the used filtration media.
It is well known to construct an air filter 8 from filtration media 14 and a rigid support 10 mounted internally within the media. The rigid support 10 is commonly thick steel wire formed in a rectangularly-shaped support 10 as shown in FIG. 2, with the filtration media 14 surrounding the support 10 as shown in the cutaway of FIG. 1. The filtration media 14 is commonly a porous, polymer, non-woven batt material, formed in a sheet-like layer. Two sheets of this material are formed into a sleeve shape by stitching 12, welding or otherwise connecting the lateral edges of two layers of filtration media that are placed with their major surfaces against one another. The area located inside of the stitches 12 is devoid of stitching so that the media layers can be separated, such as for removing the support 10. The rigid support 10 is inserted into the opening in the sleeve-shaped media 14 and the open ends of the sleeve-shaped media 14 are then welded or stitched together to retain the rigid support 10 as shown in FIG. 1.
As shown in FIG. 3, the filter media 14 is also commonly welded or stitched at reinforcement points 16, inside of the perimeter of the filter 8 to prevent the portions of the layers of media 14 that are not stitched together from moving apart, or from moving cyclically toward and away from each other, when air is forced through. This configuration provides a filter with good rigidity and good filtration characteristics, but with poor ability to remove the support 10 for recycling or disposal. In order for the components of the filter 8 shown in FIGS. 1-3 to be separated, the stitching 12 and reinforcement points 16 must all be cut or removed so that the support 10 can be separated from the media 14. However, when this is attempted with a used filter, a substantial volume of filtered particles in the media is often returned to the environment due to mechanical agitation of the filter media, which is not acceptable.